Problems getting gae-sessions to work in App Engine, error isn't helpful

Question

I've installed gae-sessions to my development environment but it doesn't seem to be storing anything. Here's a basic example:

session = get_current_session()
session.get('some_num', 3)

Then later on in some other function...

session = get_current_session()
session['some_num'] = 4

And here's the error I get in the console:

KeyError: 'some_num'

Not a very helpful error. I'm pretty sure i've followed the instructions to the letter but maybe there's something i'm missing?

edit

appengine_config.py

from gaesessions import SessionMiddleware
import os

def webapp_add_wsgi_middleware(app):
    app = SessionMiddleware(app, os.urandom(32))
    return app

Offending code

class Test(webapp.RequestHandler):
    def get(self):
        session = get_current_session()
        if session.is_active():
            # set session['some_num'] to whatever was in there or three, otherwise
            session['some_num'] = session.get('some_num', 3) 

            # later, session['some_num'] should exist and be equal to 3 ...
            assert session['some_num'] == 3

            # ... and is actually 'settable'
            session['some_num'] = 4
        else:
            self.response.out.write("Session is NOT active")

.is_active() doesn't return true.

Answer 1

Looking at the example app ( here ), it appears that all sessions start off inactive, and are automatically set to active the first time you store a value to them. You should simply be able to store a value to the session with session['foo'] = 'bar' , and it'll automatically activate the session.

Also note that you shouldn't be generating the cookie key like that. As the docs in the sample appengine_config.py say:

# suggestion: generate your own random key using os.urandom(64)
# WARNING: Make sure you run os.urandom(64) OFFLINE and copy/paste the output to
# this file.  If you use os.urandom() to *dynamically* generate your key at
# runtime then any existing sessions will become junk every time you start,
# deploy, or update your app!

Answer 2

In your code (as it stands) you don't add some_num to your session dictionary in the first place. Try:

from gaesessions import get_current_session
session = get_current_session()
if session.is_active():
    # set session['some_num'] to whatever was in there or three, otherwise
    session['some_num'] = session.get('some_num', 3) 
...

# later, session['some_num'] should exist and be equal to 3 ...
assert session['some_num'] == 3

# ... and is actually 'settable'
session['some_num'] = 4